19.4.3. Distribution of Total Impacts

Several studies have estimated the total impact (aggregated across sectors)
in different regions of the world. Table 19-4 shows aggregate,
monetized impact estimates for a doubling of atmospheric CO2 on the
current economy and population from four studies. Clearly, in all of these studies
there are substantial uncertainties about the total impacts to regions and whether
some regions will have net benefits or net damages at certain changes in global
average temperature. Most studies, however, show the following:

Developing countries, on the whole, are more vulnerable to climate change
than developed countries.

At low magnitudes of temperature change, damages are more likely to be
mixed across regions, but at higher magnitudes virtually all regions have
net damages.

The distribution of risk may change at different changes in temperature.

Developing countries tend to be more vulnerable to climate change because their
economies rely more heavily on climate-sensitive activities (particularly agriculture),
and many already operate close to environmental and climatic tolerance levels
(e.g., with respect to coastal and water resources). If current development
trends continue, few developing countries will have the financial, technical,
and institutional capacity and knowledge base for efficient adaptation (a key
reason for higher health impacts). For temperature increases of less than 2-3°C,
some regions may have net benefits and some may have net damages. If temperature
increases more than 2-3°C, most regions have net damages, and damages
for all regions increase at higher changes in global average temperature.